CVE-2020-7754 in npm-user-validate
Summary
by MITRE
This affects the package npm-user-validate before 1.0.1. The regex that validates user emails took exponentially longer to process long input strings beginning with @ characters.
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Analysis
by VulDB Data Team • 11/27/2020
The vulnerability identified as CVE-2020-7754 affects the npm-user-validate package version prior to 1.0.1, representing a significant performance degradation issue that manifests through regex processing inefficiencies. This flaw specifically targets email validation functionality within the npm package ecosystem, where the regular expression implementation exhibits exponential time complexity when processing input strings that begin with the @ character. The vulnerability demonstrates characteristics of a denial of service attack vector through resource exhaustion, as malicious actors could exploit this weakness to cause system slowdowns or complete service unavailability.
The technical root cause of this vulnerability lies in the implementation of regular expressions used for email validation, which suffers from catastrophic backtracking behavior. When input strings begin with @ characters and extend to considerable lengths, the regex engine must perform an exponential number of operations to determine whether the pattern matches, leading to dramatic performance degradation. This behavior aligns with CWE-1333, which describes weaknesses related to regular expression vulnerabilities that can cause excessive resource consumption. The specific regex pattern used in npm-user-validate fails to account for the potential for exponential backtracking, creating a scenario where legitimate validation operations become computationally infeasible for sufficiently long input strings.
The operational impact of this vulnerability extends beyond simple performance degradation, as it creates potential security risks through resource exhaustion attacks. Attackers could exploit this weakness by submitting carefully crafted long email addresses beginning with @ symbols to cause denial of service conditions in systems that rely on npm-user-validate for user input validation. This vulnerability affects any application or service that depends on this package for email validation, potentially impacting npm package management systems, user registration processes, and any other components that validate user email addresses through this specific validation library. The attack surface is particularly concerning given npm's widespread usage in node.js environments and the prevalence of email validation in web applications.
Mitigation strategies for CVE-2020-7754 should prioritize updating to version 1.0.1 or later of npm-user-validate, which contains the patched regex implementation that prevents exponential backtracking behavior. Organizations should implement input length restrictions for email validation fields to limit the potential impact of malicious inputs, while also considering alternative validation approaches that do not rely on regular expressions susceptible to catastrophic backtracking. Security teams should monitor their dependency trees for similar vulnerable packages and implement automated scanning tools to identify and remediate such issues proactively. The fix implemented in version 1.0.1 addresses the core regex implementation by either modifying the pattern to prevent backtracking or by introducing more efficient validation logic, aligning with best practices for secure regex implementation as recommended in the OWASP regex guidelines and ATT&CK technique T1496 for resource exhaustion attacks. Organizations should also consider implementing rate limiting and input sanitization measures to provide additional defense-in-depth against potential exploitation of similar vulnerabilities in other components of their software supply chain.